Probiotic agents are organisms that confer a benefit when they grow in a particular environment, often by inhibiting the growth of other biological organisms in the same environment. Examples of probiotics include bacteria and bacteriophages which can grow in the intestine, at least temporarily, to displace or destroy pathogens and provide other benefits to the host organism (Salminen et al, Antonie Van Leeuwenhoek, 70 (24): 347-358, 1996; Elmer et al, JAMA, 275:870-876, 1996; Rafter, Scand. J. Gastroenterol. 30:497-502, 1995; Perdigon et al, J. Dairy Sci., 78:1597-1606, 1995; Gandi, Townsend Lett. Doctors & Patients, pp. 108-110, January 1994; Lidbeck et al, Eur. J. Cancer Prev. 1:341-353, 1992). Probiotic preparations were systematically evaluated for their effect on health and longevity in the early 1900's (Metchnikoff, E., Prolongation of Life, Wilham Heinemann, London, 1910; republished by G.P. Putnam's Sons, New York, N.Y., 1970). Since the discovery and widespread use of antibiotics in about 1950 to treat pathological microbes, the use of probiotics has been limited.
The widespread use of antimicrobial drugs, especially broad spectrum antibiotics, has produced serious consequences. Individuals taking antibiotics often suffer from gastrointestinal upset when beneficial microorganisms in the gut are killed, thus changing the balance of the intestinal flora. This imbalance can result in vitamin deficiencies when vitamin-producing gut bacteria are killed and additional illness if a pathogenic organism overgrows and replaces the beneficial gut microorganisms. In addition, widespread antibiotic use has produced increasing numbers of antibiotic-resistant pathogenic microorganisms, including vancomycin-resistant bacteria. Microorganisms that are resistant to multiple drugs have also developed, often with multiple drug resistance spreading between species, leading to systemic infections that cannot be controlled by use of known antibiotics. Thus, there is a need for preventive and therapeutic agents that can control pathogenic microorganisms without the use of antibiotic chemicals.
Sudden Infant Death Syndrome (SIDS) refers to the sudden and unexpected death of an apparently healthy infant, typically between the ages of three weeks to five months, peaking at about three months of age. Generally, the death is due to cardiorespiratory failure in which the child dies quietly with no symptoms that would indicate grave illness before death, although infections in the few weeks before death have been observed in about 85% of SIDS victims. Although SIDS is a leading cause of infant mortality in the developed countries of the world, its cause is not well understood.
Several researchers have reported that various toxigenic bacteria and their enterotoxins are implicated in the aetiology of SIDS (Amon S. S. et al., Lancet 1: 1273-1277, 1978; Gurwith M. J. et al., Am. J. Dis. Child. 135:1104-1106, 1981; Cooperstock M. S. et al., Pediatr. 70:91-95, 1982; Donta S. & Myers M., J. Pediatr. 100:431-434, 1982; Amon S. S. et al., J. Pediat. 104(1):34-40, 1984; Murrell T. G. et al., Med. Hypoth. 22:401-413, 1987; Blackwell C. C. et al., J. Clin. Pathol. 45(11 Suppl.):20-24, 1992; Lindsay J. A. et al., Curr. Microbiol. 27:51-59, 1993; Murrell W. G. et al., J. Med. Microbiol. 39(2):114-127, 1993; Mach A. S. & Lindsay J. A., Curr. Microbiol. 28:261-267, 1994; Siarakas S. et al., Toxicon 33(5):635-649, 1995). Bacterial species implicated in SIDS include Clostridium perfringens, C. difficile, C. botulinum, Staphylococcus aureus and Escherichia coli, although the correlation between the presence of particular bacterial species and SIDS has not been entirely consistent between studies (Gurwith M. J. et al., Am. J. Dis. Child 135:1104-1106, 1981; Blackwell C. C. et al., J. Clin. Pathol. 45(11 Suppl.):20-24, 1992; Murrell W. G. et al., J. Med. Microbiol. 39(2):114-127, 1993; Lindsay J. A. et al., Curr. Microbiol. 27:51-59, 1993; Siarakas S. et al., Toxicon 33(5):635-649, 1995). Clostridium species, particularly C. perfringens and C. difficile, are most often associated with fecal samples obtained from children who have died of SIDS. Bacterial toxins found in fecal matter and serum of SIDS babies may be etiological agents of SIDS. These bacterial toxins include C. perfringens enterotoxin and alpha-toxin, Staphylococcus enterotoxin B, E. coli heat-stable toxin (STa), C. difficile toxins A and B, and C. botulinum toxin (Blackwell C. C. et al., J. Cliff. Pathol. 45(11 Suppl.):20-24, 1992; Murrell W. G. et al., J. Med. Microbiol. 39(2):114-127, 1993; Siarakas S. et al., Toxicon 33(5):635-649, 1995). C. perfringens Type A enterotoxin has been particularly implicated because of its ability to modulate cytokine production by human animal cells (Lindsay J. A., Crit. Rev. Microbiol. 22(4):257-277, 1996). Some of these toxins act synergistically (Siarakas S. et al., Toxicon 33(5):635-649, 1995). In animals, C. perfringens is responsible for death of several young species (e.g., lamb, pony) and C. difficile causes pseudomembranous colitis (Murrell T. G. C. et al. Med. Hypotheses 22:401-413, 1987; Murrell W. G. et al, J. Med. Microbiol. 39:114-127, 1993).
Although different hypotheses have been offered to explain how these bacteria and/or bacterial toxins may cause or contribute to SIDS, it is generally thought that SIDS results from a series of events in which pathogenic bacteria enter the gut, colonize and produce cytotoxin that initiates a cascade of reactions that lead to silent death (Lindsay J. A., Crit. Rev. Microbiol. 22(4):257-277, 1996; Murrell W. G. et al., J. Med. Microbiol. 39:114-127, 1993). The cytotoxin may damage intestinal tissue resulting in more efficient systemic absorption of the enterotoxin, without systemic migration of the bacteria. Moreover, intestinal injury may result in increased production of cytokines (e.g., interferon-gamma, tumor necrosis factor and interleukins) that exacerbate the effects of the toxins leading to a biochemical cascade that alters the circuits that control cardiorespiration, leading to irreversible shock and death (Lindsay J. A. et al., Curr. Microbiol. 27:51-59, 1993; Mach AS. & Lindsay J. A., Curr. Microbiol. 28:261-267, 1994). For example, toxin-induced changes in cell membrane permeability leading to abnormal levels of intracellular ions (potassium and/or calcium) in heart tissue may lead to cardiac failure. These explanations for SIDS are consistent with other studies that have shown an association between intestinal injury and the development of a septic state and distant organ failure in the absence of systemic bacterial infection (Deitch E. A. et al., Shock 1(2): 141-145, 1994).
Because SIDS occurs generally in young infants, before the immune system as fully developed, a vaccine against bacterial pathogens associated with SIDS would usually not be effective to prevent SIDS-associated infections because the infant would not produce a sufficient immune response to the immunogen. Anti-toxin antibodies (e.g., as disclosed in U.S. Pat. No. 5,599,539) have limited efficacy because they do not limit growth of the toxin-producing bacteria which can continue to produce toxin and the antibodies may produce an allergic reaction when orally administered. Thus, there is a need for preventive and therapeutic agents that can control the growth of SIDS-associated pathogenic microorganisms, without the use of antibiotics that can affect the beneficial microflora of the infant's gut or contribute to development of microbial drug resistance. Probiotics, which can be taken internally because they are generally regarded as safe, can be used replace or preclude growth of gut pathogens associated with SIDS. Moreover, because of their mode of action, probiotics do not produce antibiotic side effects or lead to drug-resistant pathogens.
Lactic acid producing bacteria (e.g., Bacillus, Lactobacillus and Streptococcus species) have been used as food additives and there have been some claims that they provide nutritional and therapeutic value (Gorbach S. L., Ann. Med. 22(1):37-41, 1990; Reid, G. et al., Clint. Microbiol. Rev. 3(4):335-344, 1990). Some lactic acid producing bacteria (e.g., those used to make yogurt) have been suggested to have antimutagenic and anticarcinogenic properties useful for preventing human tumors (Pool-Zobel B. L. et al., Nutr. Cancer 20(3):261-270, 1993; U.S. Pat. No. 4,347,240). Some lactic acid producing bacteria also produce bacteriocins which are inhibitory metabolites responsible for the bacteria's antimicrobial effects (Klaenhammer T. R., FEMS Microbiol. Rev. 12(1-3):39-85, 1993; Barefoot S. F. & Nettles C. G., J. Dairy Sci. 76(8):2366-2379, 1993).
The therapeutic use of probiotic bacteria, especially Lactobacillus strains, that colonize the gut has been previously disclosed (Winberg et al, Pediatr. Nephrol. 7:509-514, 1993; Malin et al, Ann. Nutr. Metab. 40:137-145, 1996; and U.S. Pat. No. 5,176,911).
Selected Lactobacillus strains that produce antibiotics have been disclosed as effective for treatment of infections, sinusitis, hemorrhoids, dental inflammations, and other inflammatory conditions (U.S. Pat. No. 4,314,995). L. reuteri produces antibiotics with activity against Gram negative and Gram positive bacteria, yeast and a protozoan (U.S. Pat. No. 5,413,960 and U.S. Pat. No. 5,439,678). L. casei ssp. rhamnosus strain LC-705, DSM 7061, alone or in combination with a Propionibacterium species, in a fermentation broth has been shown to inhibit yeast and molds in food and silage (U.S. Pat. No. 5,378,458). Also, antifungal Serratia species have been added to animal forage and/or silage to preserve the animal feedstuffs, particularly S. rubidaea FB299, alone or combined with an antifungal B. subtilis (strain FB260) (U.S. Pat. No. 5,371,011).
Bacillus coagulans is a non-pathogenic gram positive spore-forming bacteria that produces L(+) lactic acid (dextrorotatory) in homofermentation conditions. It has been isolated from natural sources, such as heat-treated soil samples inoculated into nutrient medium (Bergey's Manual of Systemic Bacteriology, Vol. 2, Sneath, P. H. A. et al., eds., Williams & Wilkins, Baltimore, Md., 1986). Purified B. coagulans strains have served as a source of enzymes including endonucleases (e.g., U.S. Pat. No. 5,200,336), amylase (U.S. Pat. No. 4,980,180), lactase (U.S. Pat. No. 4,323,651) and cyclo-malto-dextrin glucano-transferase (U.S. Pat. No. 5,102,800). B. coagulans has been used to produce lactic acid (U.S. Pat. No. 5,079,164). A strain of B. coagulates (referred to as L. sporogenes Sakaguti & Nakayama (ATCC 31284)) has been combined with other lactic acid producing bacteria and B. natto to produce a fermented food product from steamed soybeans (U.S. Pat. No. 4,110,477). B. coagulans strains have also been used as animal feed additives for poultry and livestock to reduce disease and improve feed utilization and, therefore, to increase growth rate in the animals (International PCT Pat. Applications No. WO 9314187 and No. WO 9411492).